Electrical stimulation of the cholinergic anti-inflammatory pathway (NCAP) by stimulation of the carotid vagus nerve been well described. For example, see U.S. Pat. Nos. 6,838,471, 8,914,114, 9,211,409, 6,610,713, 8,412,338, 8,996,116, 8,612,002, 9,162,064, 8,855,767, 8,886,339, 9,174,041, 8,788,034 and 9,211,410, each of which is herein incorporated by reference in its entirety.
Implantable electrical stimulation devices have been developed for therapeutic treatment of a wide variety of diseases and disorders. For example, implantable cardioverter defibrillators (ICDs) have been used in the treatment of various cardiac conditions. Spinal cord stimulators (SCS), or dorsal column stimulators (DCS), have been used in the treatment of chronic pain disorders including failed back syndrome, complex regional pain syndrome, and peripheral neuropathy. Peripheral nerve stimulation (PNS) systems have been used in the treatment of chronic pain syndromes and other diseases and disorders. Functional electrical stimulation (FES) systems have been used to restore some functionality to otherwise paralyzed extremities in spinal cord injury patients.
Typical implantable electrical stimulation systems may include one or more programmable electrodes on a lead that are connected to an implantable pulse generator (IPG) that contains a power source and stimulation circuitry. However, these systems can be difficult and/or time consuming to implant, as the electrodes and the IPG are usually implanted in separate areas and therefore the lead must be tunneled through body tissue to connect the IPG to the electrodes. Also, leads are susceptible to mechanical damage over time, particularly as they are usually thin and long.
Recently, small implantable neural stimulator technology, i.e. microstimulators, having integral electrodes attached to the body of a stimulator has been developed to address the disadvantages described above. This technology allows the typical IPG, lead and electrodes described above to be replaced with a single integral device. Integration of the lead has several advantages including reduction of surgery time by eliminating, for example, the need for implanting the electrodes and IPG in separate places, the need for a device pocket, the need for tunneling to the electrode site, and requirements for strain relief ties on the lead itself. Reliability may therefore be increased significantly, especially in soft tissue and across joints because active components, such as lead wires, are now part of the rigid structure and are not subject to the mechanical damage due to repeated bending or flexing over time.
There remains a need for a leadless integral device that is stably positioned on the nerve, and can provide for removal and/or replacement of the stimulation device with relative ease.
Charging and/or communication with an implant by electrical induction (e.g., via one or more inductive coils) may be well suited for use with implantable microstimulators, including those adapted for use to treat inflammation. However, induction may be difficult, particularly where the implant is located deep within the body, as may be the case with a sub-diaphragmatic implant, or where the orientation is not known or is difficult to align with. In previous iterations of the recharging portion of the system, the recharger included a coil that could be worn around a patient's neck. In this configuration, the coil is able to generate an electromagnetic field having sufficient strength to penetrate the patient's body and reach the implanted device for recharging the implanted device. While this recharging scheme is effective, it requires the patient to periodically wear a ring around their necks.
Described herein are microstimulators, charging systems, and methods of using them that may address some of the needs identified above.
Although stimulation of the vagus nerve at the upper levels has been well characterized, stimulation of the NCAP pathway at more distal sites, including sub-diaphragmatic sites has not been well characterized, and poses unique problems and opportunities.
For example, stimulation of sub-diaphragmatic sites may provide fewer adverse events and particularly possibly providing fewer undesirable cardiac effects and laryngeal effects. However, sub-diaphragmatic placement has not been characterized, and may be expected to have a lower efficacy. In addition, the NCAP pathways in sub-diaphragmatic regions may be difficult to access and provide stable placement of a microstimulator.
Also described herein are methods an apparatuses that may address the issues raised above.